修复区间打分 422 错误：Go 后端新增 runRangeRequest 结构体正确透传 start_date/end_date

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/backend/internal/handlers/run.go

@@ -56,8 +56,14 @@ func (d *Deps) RunBatch(w http.ResponseWriter, r *http.Request) {
 	_, _ = io.Copy(w, resp.Body)
 }
 
+type runRangeRequest struct {
+	Symbol    string `json:"symbol,omitempty"`
+	StartDate string `json:"start_date,omitempty"`
+	EndDate   string `json:"end_date,omitempty"`
+}
+
 func (d *Deps) RunRange(w http.ResponseWriter, r *http.Request) {
-	var req runRequest
+	var req runRangeRequest
 	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
 		writeErr(w, http.StatusBadRequest, "invalid json")
 		return